The paper you refer to (Levy et al., 2008) indeed addresses the fundamental issue of economics ‘Where Profits Come From’ but gives the wrong answer. For the formal refutation of the Levy approach see the working paper ‘Keynes’s Missing Axioms’ (2011b)

For the correct explanation see ‘The Emergence of Profit and Interest in the Monetary Circuit’ (2011a).

* See also cross-references ‘Refutation of I=S’http://axecorg.blogspot.de/2015/01/is-cross-references.htmland in particular ‘The final implosion of MMT’http://axecorg.blogspot.de/2016/10/the-final-implosion-of-mmt.html